/in/foo.cc: In function 'int main()':
/in/foo.cc:26:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i=2;i<s1.length()-1;i++) s2=s2+s1[i];
                      ~^~~~~~~~~~~~~~
/in/foo.cc:31:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (int i=2;i<s2.length();i++) s3=s3+s2[i];
                          ~^~~~~~~~~~~~
/in/foo.cc:9:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define rep for (int i=0;i<st.size();i++)
                          ~^~~~~~~~~~
/in/foo.cc:59:9: note: in expansion of macro 'rep'
         rep 
         ^~~
/in/foo.cc:70:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i=0;i<st1.size();i++)
                      ~^~~~~~~~~~~
/in/foo.cc:9:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define rep for (int i=0;i<st.size();i++)
                          ~^~~~~~~~~~
/in/foo.cc:84:9: note: in expansion of macro 'rep'
         rep 
         ^~~
/in/foo.cc:55:9: warning: label 'check' defined but not used [-Wunused-label]
         check:
         ^~~~~